1. Field of the Invention
The present invention relates generally to methods and devices for positioning and sealing concentric tubular members with respect to each other. The present invention relates more specifically to methods and devices for creating differential movement and storing residual energy of sufficient volume and magnitude for hanging, sealing, or packing the annular space between a first tubular structure, such as a well casing, and a second tubular structure such as a pipe string.
2. Description of the Related Art
There are many environments within which concentric tubular elements are utilized to conduct the flow of various fluids and the like to and from fluid sources. Oil and gas well boreholes provide an example of one such environment. In many drilling operations it is desirable to provide casing within the well and to additionally segment or segregate portions of the cased borehole in order to access various formations encountered by the well. Segregation of a cased borehole (or even an uncased well in some instances) may be accomplished by any of a number of mechanisms for sealing or packing the annular space around the inner tubular structure between that inner tubular and the outer tubular structure (the casing). In other circumstances it is additionally desirable to provide fixed contact between an inner tubular member and an outer tubular member for the purpose of suspending or hanging the weight of a pipe string or tool section at a point within the borehole other than at a surface structure.
As indicated above, there are many mechanisms and methods for sealing, packing, and/or hanging a first tubular member inside a second tubular member. Factors such as drill string weight, borehole pressure, borehole temperature, drilling fluid composition, as well as the purpose of the packing, all contribute to the selection of a mechanism and method that works best in a given environment. In some applications removal of a seal or segregation is a requirement that dictates a generally more complex mechanism. High pressures and temperatures dictate sealant surfaces that are resistant to degradation under such conditions. Most often, the strength, structure and operation of a packing mechanism is dictated by the amount of weight that the point of casing contact is called upon to support.
The placement of permanent packers and the like, in a combination of tubular elements, may involve structures that utilize mechanical compression setting tools, hydraulic pressure devices, inflatable charges, or inflatable sealing elements with cement or other materials injected therein. One result dictated by some of the various factors mentioned above has been the development of structurally heavy and complex mechanisms for the placement of a casing seal especially those intended to be removable. A large category of such packing devices comprise radial arrays of wedge elements that may be forced outward into contact with the inner walls of the casing to establish a fixation of the inner tubular with respect to the casing and in some instances to establish an annular seal between the inner tubular and the casing. There are various mechanisms for activating these wedges through manipulation of the drill string or through remote operation of hydraulic or electric devices from the surface. In many instances a longitudinal compression of the drill string (which can be accomplished in a variety of ways) acts to force plates, wedges or other movable surfaces outward from the inner tubular to make contact with the casing or outer tubular. In other designs, counter-rotation of the drill string can serve to activate (or deactivate) the outward movement of the contact wedges or plates. The general rule for such structures is one of greater and greater mechanical complexity in order to assure operation and a tight fit against the casing wall. Complexity, however, leads to unreliability and failure which, if occurring many thousands of feet underground, can result in millions of dollars of recovery and retrieval costs.
Complexity also fails in environments where multiple seal placements are required. It is often necessary in borehole operations to place a number of seals in order to adequately segregate the various formations of interest. Once a first seal has been made subsequently placed xe2x80x9clowerxe2x80x9d seals must be manipulated through the first xe2x80x9cupperxe2x80x9d seal. This means that the packer device must be smaller in initial configuration in order to fit through the first seal placement. The more complex the device the less it lends itself to reductions in size sufficient to permit such multiple seal placements.
While oil and gas drilling operations provide a prime example of the need to establish concentric tubular zones and sections, other industries and environments also have need for mechanisms of this type. Certainly other forms of drilling operations often require the placement of inner tubular structures within concentric outer tubular structures. Pipeline operations, both inside and outside plant, often require the use of concentric tubular elements and the proper sealing of such elements together, often from a remote location.
It would be desirable to have an apparatus and method for the placement, positioning and sealing of a first tubular member in a fixed position with respect to a second concentric tubular member in a manner that provides a durable seal placement that resists degradation over time and exposure to high temperature and pressure environments. It would be desirable if such a system were simple in construction so as to reduce the chances of its failure to operate when utilized at a distance from an activating mechanism. It would be desirable to define a system whose basic concepts of operation were applicable in a variety of industrial environments and a range of structural geometries.
It is therefore an object of the present invention to provide an apparatus for the placement, positioning and sealing of a first tubular member in a fixed position with respect to a second concentric tubular member.
It is an object of the present invention to provide a packing type device for the placement, positioning and sealing of tubular members in a permanent manner that resists degradation of the seal over time.
It is an object of the present invention to provide a packing type device for the placement, positioning and sealing of tubular members in a permanent manner that resists degradation of the seal when exposed to high temperature and high pressure environments.
It is a further object of the present invention to provide a sealing system for use between concentric tubular members that seals the annular space between the tubular members and fixes the position of the tubular members with respect to each other, with a seal that retains its resiliency or internal pressure over time.
It is a further object of the present invention to provide a sealing device that may be moved to a position within an outer tubular member without significant damage to the surface area associated with the seal during the placement process.
It is a further object of the present invention to provide a method for placing, positioning and sealing a first tubular member in a fixed position with respect to a second concentric tubular member.
It is a further object of the present invention to provide a seal placement method that may be implemented from a remote location but which involves a mechanical simplicity that reduces the likelihood of operational failure.
It is a further object of the present invention to provide a method for the placement of a seal between tubular members that requires only a simple structural linkage between the point of seal placement and the point from which the operation of the process is directed.
In fulfillment of these and other objectives the present invention provides an apparatus and method for the placement and sealing of a first tubular member in a fixed position with respect to a second concentric tubular member. The system of the invention utilizes an inner tubular member formed with a shallow annular depression in the tube wall at the point of sealant placement. The formation of the annular depression causes the wall of the inner tubular member to xe2x80x9cintrudexe2x80x9d into the otherwise cylindrical passage within the inner tube. On the outer surface of the first inner tubular member the depression is filled with a partially compressible fluid. The annular depression and the partially compressible fluid are then covered over by a malleable/ductile sleeve that serves to complete the cylindrical outer wall of the inner tubular member while maintaining an outside diameter less than the inside diameter of the outer tubular member. Placement of the seal involves first positioning the inner tubular member within the outer tubular member and moving the inner tube longitudinally within the outer tube until the covered annular depression is positioned at the desired sealing point. Activation of the seal involves directing a cylindrical or expanding roller displacement device through the inside of the inner tubular member to the point at which the displacement device encounters the xe2x80x9cintrusionxe2x80x9d of the wall of the inner tube caused by the annular depression formed in the inner tube wall. The displacement device is forced past the annular intrusion in a manner that pushes the wall of the inner tube outward to effectively remove the annular depression and straighten the cylindrical wall of the tube to permit the passage of the displacement device there through. At the same time the partially compressible fluid is forced to expand outward under the malleable/ductile cover in a manner that intrudes into the annular space between the inner tube and the outer tube. This expansion pushes the malleable/ductile cover into contact with the inner wall of the outer tubular member, which contact increases in area and force as the partially compressible fluid therein continues to be pressured from within by the displacement of the wall of the inner tubular member caused by the movement of the displacement device. The partially compressible fluid has a residual energy sufficient to maintain the sealing element in intimate contact with the outer casing wall.